The present invention relates to anti-extrusion rings and, more particularly, to wire encapsulated extrusion rings.
Seals have been used to isolate fluids at various pressures and temperatures. Such seals have existed for use in packing rings, seal rings, piston rings and gland structures in industrial equipment, such as cylinders, pumps, hydraulics and valves, and in oil field equipment, such as down hole tools and surface equipment, requiring seals, for example, against high pressure and low pressure liquids and gases. Typically, these seals are annular seals.
However, under pressure, such seals may be eroded or destroyed and require back-up rings to prevent extrusion of the seal rings. See, for example, U.S. Pat. No. 4,234,197, issued Nov. 18, 1982, Amancharla, et al, entitled Conduit Sealing System. Such systems, however, are bulky and require additional length; At times they require structures with different materials as back-up rings and require a modules of materials at escalating values, which must be maintained even at high temperatures, which is not possible.
Another illustration of seals, as opposed to back-up rings, used in the prior art is shown in U.S. Pat. No. 4,524,982 to Hertz, issued Jun. 25, 1985 and entitled Seal for Aggressive Environments. Hertz merely discloses elastomer-impregnated windings of asbestos yarn impregnated into an elastomer to illustrate a seal ring as opposed to a back-up ring, a sort of xe2x80x9csteel belted radialxe2x80x9d of seals. For similar encapsulated rings, see also, U.S. Pat. No. 4,423,544 to Kashmerick, issued Jan. 3, 1984 for A Method of Making Composite Gasket. For back-up rings, see also, U.S. Pat. No. 3,810,639, issued May 14, 1974, to Scanell, entitled Frangible Back-up Ring for Sealing Rings.
It is an object of the current invention to avoid the distortions and other problems of the prior art through the use of a non-homogeneous wire encapsulated anti-extrusion ring.
A wire encapsulated back-up ring is disclosed having a co-efficient of thermal expansion while the ring is under pressure which is less than or equal to the surrounding gland metal. The upper surface of the back-up ring is concave to allow pressure to energize the back-up ring. The outer and inner surfaces normally remain in contact with adjacent portions of the gland and maintain an anti-extrusion barrier for a sealing ring. The anti-extrusion element also has a lower surface adapted to mate with or be a support member behind the anti-extrusion element. If the back-up ring is not also the support member, the support member surface may have a shape as required to hold the element or elements in place. The body of the element includes two parts. The first part is a wire mesh, used for reinforcement. Such a part would typically be formed in a vee shape, but may deviate to conform to the support member. The second part is a coating of sealing material which would encapsulate the wire mesh shape. The coating may vary in thickness around the wire mesh shape. The coating thickness would depend upon the strength requirement of the seal.